Many modern motor vehicles include an air conditioning system comprising a primary circuit having a compressor, a condenser, an expansion valve, and an evaporator. In some air conditioning systems, the primary circuit further includes a receiver drier disposed between an outlet of the condenser and an inlet into the expansion valve. The receiver drier is configured to store liquid refrigerant of the air conditioning system and to remove undesired moisture from the refrigerant such as water, by using a moisture absorbent material such as a desiccant.
The receiver drier is also typically configured to remove impurities and other contaminants that may be carried by the flow of the refrigerant. Accordingly, the receiver driers of the prior art typically include some form of filter unit disposed therein and are positioned to cause the flow of the refrigerant to encounter at least a portion of the filter unit before exiting the receiver drier. The filter units used in the receiver driers of the prior art may generally include a screen element having openings formed therein for allowing the refrigerant to flow therethrough, whereas the impurities or the contaminants encountering the screen element are embedded in the screen element to prevent passage of the impurities or the contaminants. However, the entrapment of the impurities or the contaminants causes the openings of the screen element to become clogged during an extended period of use, thereby reducing an efficiency of the system including the receiver drier.
One solution to the problem of clogging of the filter unit is to increase an effective surface area of the screen elements to provide the refrigerant with an increased flow area through which to pass when encountering the screen elements. The increase in the effective surface area of the screen elements extends the useful life of the filter unit. However, the size, the shape, and the orientation the filter unit must be carefully chosen to ensure that the refrigerant flowing through the filter unit does not encounter an excessive change in pressure or velocity that could alter an operation of the air conditioning system, to ensure that the filter unit is adapted for the specific configuration of the receiver drier, and to allow the filter unit to be removable and replaceable when the effective life of the filter unit expires due to the accumulation of the impurities and the contaminants carried by the refrigerant.
Many of the receiver driers of the prior art typically include one chamber for receiving the moisture absorbent material, another distinct chamber for receiving the filter unit, and a fluid flow path fluidly coupling the chambers to each other. One possible configuration includes the fluid flow path extending along a central longitudinal axis of the receiver drier before terminating at an outlet disposed within an interior portion of the filter unit, which is in turn surrounded by a screen element of the filter unit. After entering the interior of the filter unit, the refrigerant is caused to flow in a direction radially outwardly from the outlet of the fluid flow path to encounter the screen element before exiting the chamber having the filter unit. Accordingly, the receiver driers of the prior art include an inside-to-outside flow configuration of the filter unit in accordance with the relative positioning of the two distinct chambers and the fluid flow path of the receiver drier.
However, alternative configurations of the receiver drier have been disclosed wherein the fluid flow path connecting the chambers of the receiver drier is disposed along an outer region of a housing of the receiver drier. The arrangement with the fluid flow path disposed along the outer region of the housing causes the refrigerant entering the chamber including the filter unit to initially flow into a region of the chamber disposed outside of the interior of the filter unit, in contrast to the previously described receiver driers including a centrally located fluid flow path that includes an outlet discharging into the interior of the filter unit. Therefore, the receiver drier with the fluid flow path disposed along the outer region of the housing requires an alternate configuration of the filter unit suitable for the flow of the refrigerant to enter the filter unit in a direction transverse to the longitudinal direction of the receiver drier rather than entering the filter unit in a direction parallel to the longitudinal direction of the receiver drier. One example of a receiver drier having the configuration with the fluid flow path disposed along the outer region of the housing can be found in U.S. Pat. No. 8,959,948 to Armsden et al., the disclosure of which is hereby incorporated by reference in its entirety.
It would be desirable to create a filter unit of a receiver drier for use with a condenser of an air conditioning system wherein a packaging size is minimized, an effective surface area of a screen element is maximized to maximize a useful life of the filter unit, and a configuration of the filter unit permits a refrigerant to enter and exit the filter unit in a direction transverse to a longitudinal axis of the receiver drier.